ASTM D4141/D4141M-22 PDF

SIGNIFICANCE AND USE 5.1 As with any accelerated test, the increase in rate of weathering compared to in-service exposure is material dependent. Therefore, no single acceleration factor can be used to relate two different types of outdoor weathering exposures. The weather resistance rankings of coatings provided by these two procedures may not agree when coatings differing in composition are compared. These two procedures should not be used interchangeably. 5.2 The procedures described in this practice are designed to provide greater degradation rates of coatings than those provided by fixed-angle, open-rack, outdoor exposure racks. For many products, fixed angle exposures will produce higher degradation rates than the normal end use of the material. 5.2.1 The use of Procedure A (Black Box) instead of an open-rack direct exposure is a more realistic test for materials with higher temperature end use service conditions. For many coatings, this procedure provides greater rates of degradation than those provided by 5°, equator-facing, open-rack exposures because the black box produces higher specimen temperatures during irradiation by daylight and longer time of specimen wetness. The black box specimen temperatures are comparable to those encountered on the hoods, roofs, and deck lids of automobiles parked in sunlight. The relative rates of gloss loss and color change produced in some automotive coatings by exposures in accordance with Procedure A are given in ASTM STP 781.4 5.2.2 The acceleration of degradation by weathering as described in Procedure C is produced by reflecting sunlight from ten mirrors onto an air-cooled specimen area. Approximately 1400 MJ/m2 of ultraviolet radiant exposure (295 to 385 nm) is received over a typical one-year period when samples are exposed on these devices in a central Arizona climate. This compares with approximately 333 MJ/m2 of ultraviolet radiant exposure from a central Arizona at-latitude exposure and 280 MJ/m2 of ultraviolet radiant expos... SCOPE 1.1 This practice covers two accelerated outdoor exposure procedures for evaluating the exterior weather resistance of coatings applied to substrates. 1.2 The two procedures are as follows: 1.2.1 Procedure A—Black Box Exposure. 1.2.2 Procedure C—Fresnel Reflector Rack Exposure. Note 1: Procedure B described a Heated Black Box procedure that is no longer in common use and has been removed as of the 2014 revision of this standard. 1.3 This standard does not cover all the procedures that are available to the user for accelerating the outdoor exposure of coatings. Other procedures have been used in order to provide a particular effect; however, the two procedures described here are widely used. 1.4 The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in each system are not necessarily exact equivalents; therefore, to ensure conformance with the standard, each system shall be used independently of the other, and values from the two systems shall not be combined. 1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use. 1.6 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.